2004 787 rfi wont start, please help!

[C DOO 3D]

Compression in both cylinders is 145psi, I have fuel spraying and sparks igniting. Machine turns over but wont start. I get a backfire every so often that releases a puff of smoke out the airbox. If I pull spark plugs smoke pours out as well. Machine ran before started bogging then quit. Please help, thanks.

 

[griz400]

if you have spark, fuel, and compression, and its backfiring, take a look at the rotary valve ...............

 

[C DOO 3D]

Okay thanks grizz. Do you have any idea what the timing should be set at? I can only find specs on the older rfi engines.

 

[griz400]

this will help you out https://www.youtube.com/watch?v=ULL5gfQs_UA
should be 147 deg

 

[C DOO 3D]

Alright that's what I installed it at previously today, so we are good there. Update: rechecked spark and one seemed weaker than the other and did not have a consistent spark. so I replaced the plug and it fired up! My guess is a fouled plug, which is strange because I just changed them 5 hours ago. The machine has been fouling an awful lot lately. Can bad gas cause plugs to foul? The gas has been sitting in the machine for a while.

 

[griz400]

sent you a message ..............

 

[griz400]

yep, also watch cause i blew 2 motors with an injector washing down a cylinder till we figured it all out, i replace injectors and no more problem .......you can take the bosch number right off the injector, go to http://www.fiveomotorsport.com/ and they are like 58.00 ea.

 

[C DOO 3D]

Thanks, for the info. I'm going out to buy new plugs. I'm hoping I can get a good read off them to tell me what's going on down there. I will post pics tomorrow.

 

[PGHMAN]

Griz, you state that you lost 2 motors with injectors being washed down the cylinder. Can you elaborate? I am doing a rebuild on a 98 GTX RFI and don't that to have that happen. Thanks.

 

[Coastiejoe]

I would suggest trimming back the plug wires as well since you know you are fighting a spark issue. They are a common failure.


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[Coastiejoe]

Griz, you state that you lost 2 motors with injectors being washed down the cylinder. Can you elaborate? I am doing a rebuild on a 98 GTX RFI and don't that to have that happen. Thanks.

Everything a 2-strike engine needs comes from the fuel/oil mixture. If you have a leaking injector the fuel washes the protective oil off the walls if the cylinder and creates poor lubrication. Also, too much fuel on the bearings (as in less oil) and the lubrication gets washed away and you have metal on metal.


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[griz400]

on an rfi, your air and oil come in on 1 side of motor and fuel only though injectors, (you can never premix an rfi), so, i had an injector that in mid range, was going full open, dumping fuel, washing down piston and THE OIL that was on piston and rings, and seizing motor, while, under the piston skirt, had plenty of oil along with the rest of the motor ..... so, i would suggest, 2 new injectors on your ski as well -- i have a thread called http://www.seadooforum.com/showthread.php?50814-The-RFI-(Rotax-Fuel-Injection-)-Spot -- with some info on it for you, also your fuel pump info is on there as well == reply on it also if you have any questions

 

[griz400]

Everything a 2-strike engine needs comes from the fuel/oil mixture. If you have a leaking injector the fuel washes the protective oil off the walls if the cylinder and creates poor lubrication. Also, too much fuel on the bearings (as in less oil) and the lubrication gets washed away and you have metal on metal.


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fuel doesnt see the bottom end on rfi, its shot into cylinder on other side of motor

 

[C DOO 3D]

Very interesting. When I purchased the machine I got a discount on it as it had blown rings on the PTO piston. After a hone and rebuild on the one cylinder, I realized the pto plug looked fuel fouled. The mag plug appeared to be fine. Maybe a possible connection? I guess the only true way to test if an injector is opening mid throttle would be to switch them and check the plugs...I will also trim back plug wires as well.

 

[Coastiejoe]

fuel doesn't see the bottom end on rfi, its shot into cylinder on other side of motor

You are correct as far as how things are suppose to be,,, I have seen cylinder walls washed to the point that that fuel passes by the piston rings and washes the oil away from the low end bearings. I may not have been clear, but that was the point I was trying to get across..

 

[PGHMAN]

Thanks guys for the info on the injector wash. Based on the above I plan to purchase new injectors.....hate to lose a new rebuild just over $100 for new injectors.

 

[PGHMAN]

Grizz - great thread that you posted on the necessary maintenance and concerns for an RFI. I am rebuilding a 98 GTX RFI, have sent the jugs off to Full Bore and plan to do the lower end myself once I spilt the case. Made a rookie mistake by sending out the jugs prior to pulling the PTO. Struggling with the PTO for now but I am confident I'll get with more heat and a longer cheater bar.